1. Field of the Invention
This invention is in the field of disposable dental flossing devices and particularly injection molded devices, each formed integrally as a handle plus a bow across which at least one strand of dental floss is spanned and may be manually tensioned by the user and in the field of manufacturing and packaging such dental flossing devices.
2. Background and Prior Art
This invention is in the field of devices for personal and professional dental care, particularly for removing plaque from the teeth surfaces and food particles from between teeth.
For many years teeth have been cleaned primarily by manual or power-driven brushes, and the spaces between teeth have been cleaned by a variety of methods including brushing, machine-driven jets of water, toothpicks, and the like and by flossing with the commonly available nylon dental floss and dental tape or thread or even rubber bands.
Until recently the most generally accepted objective in cleaning teeth was to remove food particles and chemicals, particularly sweets from tooth surfaces. However, now it has been established and is being taught by a growing number of dentists, orthodontists and periodontists, that the chief cause of caries (dental cavities) and a principal cause of periodontal (gum and root) disease is a bacterial plaque formation that develops on tooth surfaces. When removed, new plaque can reform in less than 24 hours. The causes of plaque development are not fully appreciated; however, a person's normal body chemistry independent of his or her particular diet can be a contributing factor.
Plaque is the name given to a bacterial substance that begins as an invisible film of micro-organisms and with saliva and foods, particularly sugars, forms a soft sticky white film on the surfaces of teeth and between teeth. If plaque is not removed daily it can develop and harden into a firmly attached substance called calculus or tartar which may cause gums to redden and swell in a condition known as gingivitis. This disease is often characterized by receding gums which causes the creation of small pockets around the teeth which trap food particles and bacteria. These pockets can enlarge if the gums become further inflamed or infected causing the bone supporting the teeth to become infected and destroyed. The weakened tissue is infection-prone and once so injured the gums cannot protect the underlying bone from the spread of this disease. Additionally, bacterial plaque produces noxious chemicals which cause cavities and irritate the gums. This is the manner in which teeth become loosened and ultimately lost, the latter stages here-described being periodontal disease.
Of the methods mentioned above for cleaning teeth, brushing is not effective to remove plaque from interdental tooth surfaces between the teeth. Water jets are not sufficiently abrasive to achieve plaque removal, though they may remove food particles very well. Also, toothpicks are too thick and cumbersome to probe and scrape between two closely adjacent surfaces. This leaves only dental floss, typically a strand of multifilamented nylon that is moved in a reciprocating action into the crack or space between the sides of two adjacent teeth. The unwaxed version of dental floss is less smooth and thus more abrasive and more effective in scraping plaque off the tooth enamel surfaces in question. However, the user of any floss has the problem of maneuvering the floss while it is under tension down between each pair of teeth. Positioning the floss is inconvenient in most teeth locations, quite difficult in many, and almost impossible in others. The procedure generally requires winding opposite ends of a strand around the middle finger of each hand respectively, then over the two index fingers of both hands which are placed into the mouth, attempting to position the span of floss between the fingers in the desired location, and finally reciprocating the floss between teeth while also moving it vertically along the tooth from tip to gum. The floss is maneuvered preferably just under the edge of the gum, held firmly against and wrapped partially around the proximal surface of the tooth and pulled over its surface toward the chewing edge.
It is known from surveys that most people, even including those who take seriously the matter of dental care and brushing regularly, do not use floss daily because the technique for use as described above is so tedious. For a number of years there have been attempts to render flossing less tedious and also to render it more effective by the development of holders onto which floss is attached. Most holders have two arms across which the floss is strung; however, secondary complications described below with the holders themselves have resulted in general non-use, and thus there has been no remedy to the original problem of promoting the regular use of floss held by hand.
One basic problem with the holders is that because they are non-disposable they are too large. Typical floss stretches on them, eventually frays and breaks during use. Whether the floss remains usable for five, twenty or more teeth depends upon the tightness of the interdental spaces and the abrasion the floss incurs. By the original manual flossing technique prior to using floss holders, the floss user merely pulled the exposed end of floss from a spool, cut off a segment and then wound the cut segment on the fingers. With certain floss holder devices the user must, for each flossing operation, obtain a length of floss, thread or carefully position it about a floss holder, pull on some part of the floss until it is in tension, and finally secure it under tension to the holder. Whether a floss supply is provided on a spool in the holder handle according to one device, or provided from a separate spool from which segments of floss are cut as needed, the remaining threading and tensioning procedure is still an inconvenient burden.
From these manually strung or manually loaded flossing devices there developed prestrung disposable flossers where a strand of floss of length to span the bow or spaced arms of the flosser had its ends secured to the arms in situ, namely at the same time the flosser handle and arms were injection molded. These devices have gained wide popularity and sales because they are convenient to use and to carry, and because they can be mass produced and sold at very low per unit cost.
Samples of prior art flossers of the type with an injection molded handle and floss prestrung at the time of molding, and disclosures of known manufacturing methods may be seen in U.S. Pat. Nos. 4,006,750, 4,016,892, 5,086,792, 5,538,023 and in the other patents cited above which are hereby incorporated herein by reference. These and similar devices, regardless of the geometric configuration of the handle, have certain useful features in common and certain troublesome features in common. These devices are light weight to use and inexpensive to manufacture, each with a bow portion formed by spaced arms and a segment of floss spanning the bow. Some configurations, as those with floss parallel to the handle, may be more convenient than others for particular users.
With some of these prior art disposable flossers having a permanently prestrung bow portion, the strand of floss becomes untaut due to stretching during use or the strand of floss was untaut due to the method of manufacture. Tensioning of the floss occurs each time the floss strand encounters resistance as it is urged to pass into the interspace between two closely or tightly adjacent teeth. After one or more uses of a strand of typical floss in a holder the floss will stretch and become slack, no longer being taut and linear between the arms or ends of the bow. Consequently, the next time the flosser with slack floss is used to penetrate the interspace between two teeth the floss takes a deep generally V-shaped configuration as penetration of the interspace is begun. This leads to two undesirable consequences. First, since the floss is not taut the bow must be moved further toward the gums than if the floss were taut. Secondly, the device becomes very difficult to use in a back and forth motion, especially when removing it.
Another reason why some prior art pre-strung flossers develop slack floss is because one or both floss ends slip slightly out of an arm of the bow during tensioning as the flosser is used. Slippage occurs when the floss is not well bonded to the holder which may occur because the plastics of the floss and handle are incompatible or because the floss and the injection molded plastic are not heated and cooled uniformly or at least not at appropriate respective temperatures and time periods for secure bonding to occur.
In conclusion, floss often stretches and subsequent attempts to use a flosser with stretched floss present difficulties or undesirable situations for the user. If the floss ends are well-anchored in the bow arms, stretching still occurs. If the floss ends are not well anchored the floss slips and slack results. Either way, after a few penetrations of interspaces many flossers have lost their tension of the floss.
For these pre-strung flossers a solution was developed to permit the user to create tautness or tension in the untaut strand by causing one or both arms of the bow to diverge from the other, this being achieved by the user squeezing appropriate parts of the dental floss holder between his/her thumb and one or more fingers. Flossers of the type which are designed to receive a fresh new strand of floss obviously can have each new strand applied tautly and thus do not incur the above-discussed stretching or looseness problem; however, new strands would have to be installed repeatedly.
In some tensioning flossers the users fingers must press one or more surfaces. Since economic factors lead to minimizing plastic and size, these flossers tend to be made of plastic having thin edges which cause pain when pressed. Alternative shapes, such as thickened edges or boxed three-dimensional shapes are more costly to make. U.S. Pat. No. 5,388,600 for example, while not a tensioning flosser has a three-dimensional boxed construction to provide a large gripping, surface, in addition to providing for stacking.
In the new invention I have identified problems and discovered solutions in the forms of a new device and a new method of manufacturing these devices, as set forth below.